For a variety of medical applications and the like, cellulosic materials such as, for example, cotton gauze are employed. Such materials must be sterilized; and, as is well known, adequate sterilization of such cellulosic materials can be accomplished by either (1) exposure to radiation dosage levels sufficient to cause biological death or (2) treatment with chemicals such as ethylene oxide. Although sterilization by radiation is often considered preferable to sterilizing cellulosic material by chemical treatment, particularly where large volume products are involved, cellulosic products (e.g., cotton gauze) often discolor during radiation sterilization. Thus, although completely sterilized, the product has an unclean cosmetic appearance and, therefore, is commercially undesirable. It is believed that one of the causes of the discoloration is the formation of free radicals (e.g., lower molecular weight polysaccharides) in the cellulosic material which gives the material a yellow appearance. Although the presence of the free radicals does not affect the sterility of the cellulosic material, its coloring of the material often affects the consumer's opinion of the quality or cleanliness of the product which it comprises.
Whatever the reason for the discoloration, it is known that discoloration which might otherwise occur during the sterilizing irradiation of cellulosic material can be prevented by controlling the water content of the cellulosic material during such irradiation. For example, in the Minutes of the International Conference in Vienna, Apr. 1-4, 1974 published by Multiscience Publication, Ltd., Montreal, Canada and entitled "Technical Developments and Prospects of Sterilization Ionizing Radiation", an article by W. C. Bradbury entitled "Physical and Chemical Effects of Ionizing Irradiation on Cellulosic Material" reports that at a water content by weight greater than 6% it is difficult to visually distinguish irradiated cellulosic material from untreated cellulosic material. It is also known that controlling the radiation dosage can reduce the radiation-induced discoloration of the cellulosic material.
Nevertheless, and despite some minimization of the problem by suitable adjustment of the radiation conditions employed during sterilization, the yellowing problem discussed herein remains. More particularly, it has been observed that, in some fashion, storage and handling seem to exacerbate the problem. As far as has been ascertained, prior work in this field has not even adequately exposed the principal causes of this problem, much less how such causes can be satisfactorily minimized or even eliminated.